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Refactor ChangeVarNodesExtended() using the custom callback
fc069a3 implemented Self-Join Elimination (SJE) and put related logic to ChangeVarNodes_walker(). This commit provides refactoring to remove the SJE-related logic from ChangeVarNodes_walker() but adds a custom callback to ChangeVarNodesExtended(), which has a chance to process a node before ChangeVarNodes_walker(). Passing this callback to ChangeVarNodesExtended() allows SJE-related node handling to be kept within the analyzejoins.c. Reported-by: Richard Guo <guofenglinux@gmail.com> Discussion: https://postgr.es/m/CAMbWs49PE3CvnV8vrQ0Dr%3DHqgZZmX0tdNbzVNJxqc8yg-8kDQQ%40mail.gmail.com Author: Andrei Lepikhov <lepihov@gmail.com> Author: Alexander Korotkov <aekorotkov@gmail.com>
1 parent fb21ed6 commit 250a718

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4 files changed

+192
-124
lines changed

4 files changed

+192
-124
lines changed

‎src/backend/optimizer/plan/analyzejoins.c

Lines changed: 145 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -74,6 +74,8 @@ static bool is_innerrel_unique_for(PlannerInfo *root,
7474
List *restrictlist,
7575
List **extra_clauses);
7676
static int self_join_candidates_cmp(const void *a, const void *b);
77+
static bool replace_relid_callback(Node *node,
78+
ChangeVarNodes_context *context);
7779

7880

7981
/*
@@ -397,7 +399,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
397399
{
398400
Assert(subst > 0);
399401

400-
ChangeVarNodes((Node *) sjinf->semi_rhs_exprs, relid, subst, 0);
402+
ChangeVarNodesExtended((Node *) sjinf->semi_rhs_exprs, relid, subst,
403+
0, replace_relid_callback);
401404
}
402405
}
403406

@@ -469,7 +472,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
469472
sjinfo->ojrelid, subst);
470473
Assert(!bms_is_empty(phv->phrels));
471474

472-
ChangeVarNodes((Node *) phv->phexpr, relid, subst, 0);
475+
ChangeVarNodesExtended((Node *) phv->phexpr, relid, subst, 0,
476+
replace_relid_callback);
473477

474478
Assert(phv->phnullingrels == NULL); /* no need to adjust */
475479
}
@@ -523,7 +527,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
523527
}
524528

525529
if (subst > 0)
526-
ChangeVarNodes((Node *) otherrel->lateral_vars, relid, subst, 0);
530+
ChangeVarNodesExtended((Node *) otherrel->lateral_vars, relid,
531+
subst, 0, replace_relid_callback);
527532
}
528533
}
529534

@@ -757,7 +762,8 @@ remove_rel_from_eclass(EquivalenceClass *ec, SpecialJoinInfo *sjinfo,
757762
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
758763

759764
if (sjinfo == NULL)
760-
ChangeVarNodes((Node *) rinfo, relid, subst, 0);
765+
ChangeVarNodesExtended((Node *) rinfo, relid, subst, 0,
766+
replace_relid_callback);
761767
else
762768
remove_rel_from_restrictinfo(rinfo, relid, sjinfo->ojrelid);
763769
}
@@ -1548,7 +1554,8 @@ update_eclasses(EquivalenceClass *ec, int from, int to)
15481554
em->em_jdomain->jd_relids = adjust_relid_set(em->em_jdomain->jd_relids, from, to);
15491555

15501556
/* We only process inner joins */
1551-
ChangeVarNodes((Node *) em->em_expr, from, to, 0);
1557+
ChangeVarNodesExtended((Node *) em->em_expr, from, to, 0,
1558+
replace_relid_callback);
15521559

15531560
foreach_node(EquivalenceMember, other, new_members)
15541561
{
@@ -1582,7 +1589,8 @@ update_eclasses(EquivalenceClass *ec, int from, int to)
15821589
continue;
15831590
}
15841591

1585-
ChangeVarNodes((Node *) rinfo, from, to, 0);
1592+
ChangeVarNodesExtended((Node *) rinfo, from, to, 0,
1593+
replace_relid_callback);
15861594

15871595
/*
15881596
* After switching the clause to the remaining relation, check it for
@@ -1677,6 +1685,118 @@ add_non_redundant_clauses(PlannerInfo *root,
16771685
}
16781686
}
16791687

1688+
/*
1689+
* A custom callback for ChangeVarNodesExtended() providing
1690+
* Self-join elimination (SJE) related functionality
1691+
*
1692+
* SJE needs to skip the RangeTblRef node
1693+
* type. During SJE's last step, remove_rel_from_joinlist() removes
1694+
* remaining RangeTblRefs with target relid. If ChangeVarNodes() replaces
1695+
* the target relid before, remove_rel_from_joinlist() fails to identify
1696+
* the nodes to delete.
1697+
*
1698+
* SJE also needs to change the relids within RestrictInfo's.
1699+
*/
1700+
static bool
1701+
replace_relid_callback(Node *node, ChangeVarNodes_context *context)
1702+
{
1703+
if (IsA(node, RangeTblRef))
1704+
{
1705+
return true;
1706+
}
1707+
else if (IsA(node, RestrictInfo))
1708+
{
1709+
RestrictInfo *rinfo = (RestrictInfo *) node;
1710+
int relid = -1;
1711+
bool is_req_equal =
1712+
(rinfo->required_relids == rinfo->clause_relids);
1713+
bool clause_relids_is_multiple =
1714+
(bms_membership(rinfo->clause_relids) == BMS_MULTIPLE);
1715+
1716+
/*
1717+
* Recurse down into clauses if the target relation is present in
1718+
* clause_relids or required_relids. We must check required_relids
1719+
* because the relation not present in clause_relids might still be
1720+
* present somewhere in orclause.
1721+
*/
1722+
if (bms_is_member(context->rt_index, rinfo->clause_relids) ||
1723+
bms_is_member(context->rt_index, rinfo->required_relids))
1724+
{
1725+
Relids new_clause_relids;
1726+
1727+
ChangeVarNodesWalkExpression((Node *) rinfo->clause, context);
1728+
ChangeVarNodesWalkExpression((Node *) rinfo->orclause, context);
1729+
1730+
new_clause_relids = adjust_relid_set(rinfo->clause_relids,
1731+
context->rt_index,
1732+
context->new_index);
1733+
1734+
/*
1735+
* Incrementally adjust num_base_rels based on the change of
1736+
* clause_relids, which could contain both base relids and
1737+
* outer-join relids. This operation is legal until we remove
1738+
* only baserels.
1739+
*/
1740+
rinfo->num_base_rels -= bms_num_members(rinfo->clause_relids) -
1741+
bms_num_members(new_clause_relids);
1742+
1743+
rinfo->clause_relids = new_clause_relids;
1744+
rinfo->left_relids =
1745+
adjust_relid_set(rinfo->left_relids, context->rt_index, context->new_index);
1746+
rinfo->right_relids =
1747+
adjust_relid_set(rinfo->right_relids, context->rt_index, context->new_index);
1748+
}
1749+
1750+
if (is_req_equal)
1751+
rinfo->required_relids = rinfo->clause_relids;
1752+
else
1753+
rinfo->required_relids =
1754+
adjust_relid_set(rinfo->required_relids, context->rt_index, context->new_index);
1755+
1756+
rinfo->outer_relids =
1757+
adjust_relid_set(rinfo->outer_relids, context->rt_index, context->new_index);
1758+
rinfo->incompatible_relids =
1759+
adjust_relid_set(rinfo->incompatible_relids, context->rt_index, context->new_index);
1760+
1761+
if (rinfo->mergeopfamilies &&
1762+
bms_get_singleton_member(rinfo->clause_relids, &relid) &&
1763+
clause_relids_is_multiple &&
1764+
relid == context->new_index && IsA(rinfo->clause, OpExpr))
1765+
{
1766+
Expr *leftOp;
1767+
Expr *rightOp;
1768+
1769+
leftOp = (Expr *) get_leftop(rinfo->clause);
1770+
rightOp = (Expr *) get_rightop(rinfo->clause);
1771+
1772+
/*
1773+
* For self-join elimination, changing varnos could transform
1774+
* "t1.a = t2.a" into "t1.a = t1.a". That is always true as long
1775+
* as "t1.a" is not null. We use qual() to check for such a case,
1776+
* and then we replace the qual for a check for not null
1777+
* (NullTest).
1778+
*/
1779+
if (leftOp != NULL && equal(leftOp, rightOp))
1780+
{
1781+
NullTest *ntest = makeNode(NullTest);
1782+
1783+
ntest->arg = leftOp;
1784+
ntest->nulltesttype = IS_NOT_NULL;
1785+
ntest->argisrow = false;
1786+
ntest->location = -1;
1787+
rinfo->clause = (Expr *) ntest;
1788+
rinfo->mergeopfamilies = NIL;
1789+
rinfo->left_em = NULL;
1790+
rinfo->right_em = NULL;
1791+
}
1792+
Assert(rinfo->orclause == NULL);
1793+
}
1794+
return true;
1795+
}
1796+
1797+
return false;
1798+
}
1799+
16801800
/*
16811801
* Remove a relation after we have proven that it participates only in an
16821802
* unneeded unique self-join.
@@ -1725,7 +1845,8 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
17251845
foreach_node(RestrictInfo, rinfo, joininfos)
17261846
{
17271847
remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
1728-
ChangeVarNodes((Node *) rinfo, toRemove->relid, toKeep->relid, 0);
1848+
ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
1849+
0, replace_relid_callback);
17291850

17301851
if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
17311852
jinfo_candidates = lappend(jinfo_candidates, rinfo);
@@ -1743,7 +1864,8 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
17431864
restrictlist);
17441865
foreach_node(RestrictInfo, rinfo, toRemove->baserestrictinfo)
17451866
{
1746-
ChangeVarNodes((Node *) rinfo, toRemove->relid, toKeep->relid, 0);
1867+
ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
1868+
0, replace_relid_callback);
17471869

17481870
if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
17491871
jinfo_candidates = lappend(jinfo_candidates, rinfo);
@@ -1785,7 +1907,8 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
17851907
{
17861908
Node *node = lfirst(lc);
17871909

1788-
ChangeVarNodes(node, toRemove->relid, toKeep->relid, 0);
1910+
ChangeVarNodesExtended(node, toRemove->relid, toKeep->relid, 0,
1911+
replace_relid_callback);
17891912
if (!list_member(toKeep->reltarget->exprs, node))
17901913
toKeep->reltarget->exprs = lappend(toKeep->reltarget->exprs, node);
17911914
}
@@ -1829,14 +1952,18 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
18291952
* Replace varno in all the query structures, except nodes RangeTblRef
18301953
* otherwise later remove_rel_from_joinlist will yield errors.
18311954
*/
1832-
ChangeVarNodesExtended((Node *) root->parse, toRemove->relid, toKeep->relid, 0, false);
1955+
ChangeVarNodesExtended((Node *) root->parse, toRemove->relid, toKeep->relid,
1956+
0, replace_relid_callback);
18331957

18341958
/* Replace links in the planner info */
18351959
remove_rel_from_query(root, toRemove, toKeep->relid, NULL, NULL);
18361960

18371961
/* At last, replace varno in root targetlist and HAVING clause */
1838-
ChangeVarNodes((Node *) root->processed_tlist, toRemove->relid, toKeep->relid, 0);
1839-
ChangeVarNodes((Node *) root->processed_groupClause, toRemove->relid, toKeep->relid, 0);
1962+
ChangeVarNodesExtended((Node *) root->processed_tlist, toRemove->relid,
1963+
toKeep->relid, 0, replace_relid_callback);
1964+
ChangeVarNodesExtended((Node *) root->processed_groupClause,
1965+
toRemove->relid, toKeep->relid, 0,
1966+
replace_relid_callback);
18401967

18411968
adjust_relid_set(root->all_result_relids, toRemove->relid, toKeep->relid);
18421969
adjust_relid_set(root->leaf_result_relids, toRemove->relid, toKeep->relid);
@@ -1919,8 +2046,10 @@ split_selfjoin_quals(PlannerInfo *root, List *joinquals, List **selfjoinquals,
19192046
* when we have cast of the same var to different (but compatible)
19202047
* types.
19212048
*/
1922-
ChangeVarNodes(rightexpr, bms_singleton_member(rinfo->right_relids),
1923-
bms_singleton_member(rinfo->left_relids), 0);
2049+
ChangeVarNodesExtended(rightexpr,
2050+
bms_singleton_member(rinfo->right_relids),
2051+
bms_singleton_member(rinfo->left_relids), 0,
2052+
replace_relid_callback);
19242053

19252054
if (equal(leftexpr, rightexpr))
19262055
sjoinquals = lappend(sjoinquals, rinfo);
@@ -1956,7 +2085,8 @@ match_unique_clauses(PlannerInfo *root, RelOptInfo *outer, List *uclauses,
19562085
bms_is_empty(rinfo->right_relids));
19572086

19582087
clause = (Expr *) copyObject(rinfo->clause);
1959-
ChangeVarNodes((Node *) clause, relid, outer->relid, 0);
2088+
ChangeVarNodesExtended((Node *) clause, relid, outer->relid, 0,
2089+
replace_relid_callback);
19602090

19612091
iclause = bms_is_empty(rinfo->left_relids) ? get_rightop(clause) :
19622092
get_leftop(clause);

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